Predictions of the Electronic Structure and Related Properties of Cubic Calcium Hexaboride (CaB6)

摘要

We present theoretical calculations of the electronic structure and related properties of calcium hexaboride (CaB6) in the zinc-blende structure. Our nonrelativistic calculations employed a local density functional approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism that implemented the ab initio Bagayoko, Zhao, and Williams (BZW) method (Bagayoko et. al 1999). The BZW procedure avoids a recently identified spurious effect. This effect, inherent to the use of basis sets in variational calculations, has plagued ab-initio calculations of electronic properties of semiconductors since their inception. Unlike previous calculations, there is an agreement between our findings and experimental results. In particular, our implementation of the ab initio BZW method led to a calculated, direct, band gap of 0.87 eV for CaB6 at the X point. The BZW procedure has so far been unfailingly successful in reproducing or predicting the correct band gaps of semiconductors using density functional potentials. Key words: calcium hexaboride, density functional theory, electronic structure, band gap, semiconductor, BZW method.